Date: Jun 14, 2009 1:31 PM
Author: David W. Cantrell
Subject: Re: A single term formula for calculating the circumference of ellipse
Shahram Zafary <shahram_zafary@yahoo.com> wrote:> Hello dear Mr. Cantrell.> Thanks a lot, for your really exact comments on my formula.> I am really grateful and hope you permit me contact you again about this> formula and some same findings that I found out before

Dear Mr. Zafary,

You are certainly welcome to contact me using my sigmaxi.net email address.

I mentioned your nice formula to Gerard Michon recently, and he has nowadded a section about it on his Numericana site. See

<www.numericana.com/answer/ellipse.htm#zafary>.

Note that Gerard found a very nice alternative way of writing yourapproximation: The quantity h = ((a - b)/(a + b))^2 often appears indealing with the perimeter of an ellipse. Using h, your approximation canbe written simply as

pi (a + b) (4/pi)^h

Although I really liked your approximation before, I like it even more inthe form above!